[API reference](https://evolu.dev/docs/api-reference) › [@evolu/common](https://evolu.dev/docs/api-reference/common) › [local‑first/Evolu](https://evolu.dev/docs/api-reference/common/local-first/Evolu) › AppName

```ts
const AppName:  brand(
  "AppName",
  UrlSafeString,
  (value) =>
    value.length >= 1 && value.length <= 41
      ? ok()
      : err<AppNameError>({ type: "AppName", value }),
  (error) =>
    The value ${JSON.stringify(error.value)} is not between 1 and 41 characters.,
) ;
```

Defined in: [packages/common/src/local-first/Evolu.ts:301](https://github.com/evoluhq/evolu/blob/5f9c0dbc31cd8a6f89f27f8f5938f8559e7b061e/packages/common/src/local-first/Evolu.ts#L301)

Application name.

Evolu uses AppName as the base prefix for [Evolu.name](https://evolu.dev/docs/api-reference/common/local-first/Evolu/interfaces/Evolu#name). The final
instance name is derived per [AppOwner](https://evolu.dev/docs/api-reference/common/local-first/Owner/interfaces/AppOwner) as
`${appName}-${createIdFromString(appOwner.id)}`.

Uses the same safe alphabet as [UrlSafeString](https://evolu.dev/docs/api-reference/common/Type/variables/UrlSafeString) (letters, digits, `-`,
`_`) and must be between 1 and 41 characters.